Method of casting



March 14, 1950 w, MA 'A H 2,500,556

METHOD OF CASTING Filed April 24, 1946 2 Sheets-Sheet l INVENTOR yew WMAL c// MW ATTO NEY March 14, 1950 J. w. MALLACH METHOD OF CASTING 2Sheets-Sheet 2 Filed April 24, 1946 INVENTOR J05PHwLACH BY AT ORNEYPatented Mar. 14, 1950 UNITED STATES PATENT OFFICE 2,500,556 ma'rnon orcas'rmc Joseph W. Mallach, Lime Rock, Conn., assignor to Budds AeroCastings, Incorporated, Canaan, Conn., a corporation of ConnecticutApplication April 24, 1946, Serial No. 664,560

4 Claims. 1

The invention relates to improvements in pressure casting methods asapplied to the molding of nonferrous metals in particular.

Conventional die casting methods are adapted to high speed production,but the castings are not very strong, large castings cannot readily beproduced, and the process is subject to other limitations recognized inthe art. Conventional permanent mold casting is adapted to production ofsomewhat larger castings, but is slower in operation and does notproduce as good a surface finish or maintain as close tolerances onfinished sizes. It, too, is subject to other limitations recognized inthe art. Ordinary sand casting produces inferior surface finish andrequires machining wherever close tolerances or smooth surfaces arerequired. This process is very slow and requires renewal of the molds,adding to the expense of castings so produced.

The primary object of my invention is to provide a new molding methodwhich combines advantageous features of these several older methodswhile eliminating certain of the disadvantages of each. In particular Ihave sought to combine the feature of rapid production with strength,close tolerance, accuracy of detail and good surface finish in thecastings produced. Other objects and advantages will appear as thedescription proceeds.

I am aware that attempts have been made heretofore to achieve somewhatsimilar objects by so-called pressure casting methods wherein moltenmetal is forced into a metal mold by a plunger, or the parts of a metalmold are forced toward one another after the metal is cast but stillfluid, or a hammer blow effect is secured by suddenly applying highpressure to cast metal in a sludge state. None of these expedients hasfound general acceptance in the art, although perhaps being useful forspecial purposes of limited application.

I have discovered in the molding of aluminum and other nonferrous metalsthat if the metal is flowed through a mold while parts of the mold areseparated slightly, and the mold parts are closed during this operation,castings of supermetal although the metal may still be in motion throughthe mold to a certain extent as the mold parts begin to come together,and even during substantially the entire mold closing operation. Themetal is thus literally stopped in its tracks" by the mold closing stepin conjunction with the freezing of the metal. This produces a strong,dense casting with excellent surface finish and conforming to closetolerance Yet the method is extremely simple and rapid in operation,contributing to low cost of product. This low cost is further abetted bythe circumstance that little if any machining is required on castings soproduced. I have found that it is even possible to produce castingshaving fine double or triple threads which will mate perfectly withoutmachining as, for example, in tiny parts used on photographic cameras. Iam not aware of the possibility of accomplishing such remarkable resultsby any methods known to the art prior to the time of my invention.

In the drawings:

Fig. 1 is a central vertical cross-sectional view through one form ofapparatus adapted for practicing my improved method in its preferredform or otherwise. are shown in the position which they occupy at thebeginning of the pouring of the metal.

Figs. 2 and 3 are similar views of the same apparatus. However Fig. 2shows parts of the mold die in the position which they occupy at anintermediate stage of the method. whereas Fig. 3 shows parts of the molddie in their fully closed positions.

The apparatus which I have selected for the purpose of illustrating myinvention is designed more particularly forthe molding of precisiongears having smooth finished teeth as cast and capable of being usedwithout machining or with minimum surface finishing treatment.

The mold consists of a metal die comprising in its general arrangement alower die member 4, a stationary upper die member 5, and movable upperdie members Ii and I, the upper and lower die members coacting to form acasting cavity 8. A pouring opening 9 in upper die member 5 communicateswith a feeder or feeders l0 gated to the casting cavity. At the oppositeside of the casting cavity a runner or runners ll lead to a riser orrisers l2 formed by the upper and lower die members 5 and I.

The lower die is suitablymounted on the bed l3 of a casting machine andis secured thereto,

for example by means of clamps II. (The draw ings have been simplifiedby showing only one In this view parts of the mold die clamp but it willbe appreciated that a series of such clamps ordinarily will beemployed.) A guide pin or pins l received in aligned apertures of thedie members 4 and 5 provide proper registry between these parts.

The movable upper die part 6 has a sliding fit in an opening "5 of theupper die member 5. This opening may be of cylindrical form as where agear casting is to be produced. The upper end of the die member 6 has alateral flange I! overlying the 'upper surface of die member 5. Theopposed faces of this flange and die member 5 are recessed as shown toreceive a number of coil springs is which serve to hold movable diemember Ii in the slightly raised or withdrawn position shown in Fig. 1.This upward movement of die member 6 is limited in its extent by contactwith the inwardly projecting flange IQ of the retaining ring 20 securedto the stationary die member 5.

The other movable die member 1 slides in an opening 2| of the die member6 and forms a hub punch for the gear casting. Opposed to the opening 2|is an opening 22 in the lower die member 4 to receive the hub core 23.The hub core has a flange 25 at its lower end for limiting its upwardmovement. This flange part of the hub core slides in a housing 26secured to the lower die member 4 or to the bed l3 of the machine bybolts or otherwise. A coil spring 21 arranged within housing 26 bears atone end against the base 28 of the housing and at the other end againstthe hub core 23, holding it normally in the position shown in Fig. 1.

Suitable power means are provided for operating the movable die members6 and I to bring them successively into the positions illustrated inFigs. 2 and 3. In the construction illustrated the ram 29 of a hydraulicpress is coupled to the hub punch as by means of a coupling 30 securedto the ram 29 by tapered lock pin 3! and to the upset end 32 of the hubpunch as by the set screw 33.

The hub punch preferably is provided with a I tapered end 3 for forminga finished bore in the hub of the gear casting to be produced.

The molding operation While parts of the die are separated from theirfully closed positions, molten metal is flowed through the mold. This isillustrated diagramv matically in Fig. 1 wherein 35 illustrates a ladletilted to pouring' position. The metal flows through the feeders, gates,casting cavity and on into the riser l2 as indicated by the arrows.While the metal is flowing through the mold, the mold parts are movedtoward their fully closed positions. At least an initial fraction ofthis closing movement is performed while the metal is flowing throughthe mold, and in accordance with my' preferred method the closinmovement is substantially entirely performed while the metal is flowingthrough the mold, and also after the mold is completely fllled withmetal. This is the condition illustrated in the drawings.

During the closing movements of the mold parts, one or more of themovable parts may be advanced toward closing position ahead of one ormore of the remaining movable parts. Thus it will be observed withreference to Fig. 2 that the initial closing movement affects only thehub punch 1 which, as it advances through the mold cavity, pushes thehub core 23 ahead of it. Upon engagement of the base of coupling 30 withthe top of mold part 6, this part advances together withthe hub punch Ifrom the position shown in Fig. 2 and these two members 6 and 1 continue to move as a unit until they reach the final position shown inFig. 3.

It is important that the flow of the metal through the mold be continuedduring at least a substantial part of the mold closing movement. Thecontinued flow of the metal through the mold during the initial closingmovement is indicated by the arrows in Fig. 2. At this point if desiredthe rate of pouring of the metal may be decreased, and if suchsufiicient head of metal has been built up in the pouring opening 9,pouring may be discontinued at this point. However the metal may stillcontinue to flow through the casting cavity to a certain extent asindicated diagrammatically by the smaller number of arrows in Fig. 3 dueto the differential in head between the risers 9 and 12. At the momentof application of the pressure produced by the closing of the mold partsthe metal should be at a temperature approaching its solidus. Thus themetal within the casting cavity is subjected to high pressure just asits flow through the mold is being arrested due to solidification. Themaintenance of this particular relationship of the mold closing step tothe freezing of the metal as it flows through the mold produces a strongdense casting with exceptionally fine surface finish, and closetolerances can be readily maintained. The operation is rapid and thecost is low.

My process is applicable to the production of very small castings aswell as to castings of considerable size. It will be understood that theconstruction of the mold may vary widely in accordance with the natureof the casting, use of cores, tolerance requirements, etc. Generallyspeaking, the moving parts of the die should be arranged to applypressure at or closely adjacent to those portions of the casting whichare to be finished to the closest tolerances-that is, the. portionswhich with ordinary casting operations would need to be machined. Thedie parts themselves preferably are made of hard- "ened steel but ifdesired can be made of other materials.

My process is particularly advantageous in the molding of nonferrousmetalsv Excellent results have been obtained in the casting of aluminumand magnesium alloys, and it has been found possible to produce partswhich do not have to be machined. This is true even in the case of smallcastings which have threaded engagement with one another.

The terms and expressions which I have employed are used in adescriptive and not a limiting sense, and I have no intention ofexcluding such equivalents of the invention described, or of portionsthereof, as fall within the purview of the claims.

I claim:

1. The method of casting metals which comprises flowing the metalthrough and beyond a mold cavity having at least one pouring openingvbetween the closing movement and the freezing of the metal serving toproduce a strong dense casting with fine surface detail.

2. The method of casting metals which comprises fiowing the metal into amold cavity having at least one riser leading therefrom while parts ofthe mold are separated from their fully closed positions, and moving themold parts to their fully closed positions while the metal at theentrance to the mold cavity is free to move outwardly for displacementof excess metal from the mold cavity, at least a fraction of the closingmovement being performed while the metal is near its freezing point andafter the mold is completely filled with metal so as to subject themetal within the mold cavity to pressure just as its fiow is beingarrested due to solidification, maintenance of the defined relationshipbetween the closing movement and the freezing of the metal serving toproduce a strong dense casting with fine surface detail.

3. The method of castingmetals which comprises flowing the metal throughand beyond a mold cavity while parts of the mold are separated fromtheir fully closed positions, and moving the mold parts to their fullyclosed positions, at least a fraction of the closing movement beingperformed while the metal is near its freezing point and after the moldis completely filled with metal so as to subject the metal within themold cavity to pressure just as its fiow into at least one riser isbeing arrested due to solidification, maintenance of the definedrelationship between the closing movement and the freezing of the metalserving to produce a strong dense casting with fine surface detail.

4. The method of casting metals which comprises flowing the metal bygravity into a mold cavity having at least one riser leading therefromwhile parts of the mold are separated from their fully closed positions,and moving the mold parts to their fully closed positions, at least afraction of the closing movement being performed while the metal is nearits freezing point and after the mold is completely filled with metal soas to subject the metal within the mold cavity to pressure just as itsflow by gravity into at least one riser is being arrested due tosolidification,'maintenance of the defined relationship between theclosing movement and the freezing of the metal serving to produce astrong dense casting with fine surface detail.

JOSEPH W. MALLACH.

REFERENCES CITED The following references are of record in th file ofthis patent:

UNITED STATES PATENTS Number Name Date 67,227 Tarr July 30, 1867 70,486Whitaker Nov. 5, 1867 1,243,714 Craig Oct. 23, 1917 1,347,728 Wills July27, 1920 1,387,864 Pepper Aug. 16, 1921 1,699,120 Reinhardt Jan. 15,1929 2,061,765 Guyot 'Nov. 24, 1936 2,181,157 Smith Nov. 28, 19392,356,338 Misfeldt Aug. 22, 1944 2,391,182 Misfeldt Dec. 18, 1945FOREIGN PATENTS Number Country Date 643,691 France May 21, 1928

